Regional circulation in the Bay of Biscay

Regional circulation

Contact: N. Ayoub, P. De Mey, F. Lyard, F. Birol

The Bay of Biscay circulation is primarily constrained by its specific bathymetric features: a narrow continental shelf along the northern Iberian coast, a shelf with an increasing width towards the north opening to the English Chanel and to the Celtic Sea, and an 'abyssal plain' with typical depths of ~4500 m.

Bay of Biscay is a macro-tidal region; the interactions between the slope and the tides lead to the generation of internal tides at, at least, two main sites: the Armorican slope and in Galicia. As Bay of Biscay is opened on the North Atlantic, the circulation and water masses in the abyssal plain are directly influenced by the circulation in the North-east Atlantic. The circulation is weakly anticyclonic (a few cm/s). The largest currents are found along the slope, with some significant seasonal variability (e.g. the Iberian Poleward Current (IPC) and the ‘Navidad’ events. A significant mesoscale activity is found in the center of the Bay of Biscay. Anticyclones with a timelife of ~ 1-year are observed to drift slowly westward and have been reported as SWODDIES (Slope Water Oceanic eDDIES).

Over the shelf, the currents are more variable and are mainly induced by density gradients or by wind. The other main features of the circulation in the Bay of Biscay are wind driven (e.g. upwelling) or due to the rivers runoffs. High-frequency atmospheric variability induces some strong surface variability in the near inertial band. As a result the surface circulation appears as a combination of complicated patterns because of the different spatial and time scales of variability that characterized them.

Our research on the regional circulation is based on numerical simulations and in situ and satellite data. We are running the SYMPHONIE model on different configurations. Within the MyOcean project we have participating to the analysis of simulations with the NEMO model in the IBI (Irish Biscay Iberian) configuration.

Recent work on the dynamics in the Bay of Biscay and its representation in regional simulations: